1. Field of the Invention
This invention relates to an optical recording medium, and more particularly, to an optical recording medium having an optical wave guide path. This invention also relates to an optical reproducing apparatus capable of reproducing recorded information from an optical wave guide path recording medium of the present invention.
2. Discussion of the Related Art
In Japanese Unexamined Patent Publication No. Hei 2-210627, a wave guide path recording medium is disclosed which has a flat body in which a plurality of channel type ridge optical wave guide paths are arranged in parallel on a substrate. In the optical wave guide paths, refractive index discontinuous portions, for example concave portions, are disposed for generating a plurality of reflected wave guide lights having different amplitudes and phases in the optical wave guide paths corresponding to information to be recorded.
In addition, different types of optical wave guide path recording medium have been proposed, including a disc type formed by winding a flat body having an optical wave guide path, a tape-shaped type, a card-stacked block type and the like. Reproduction of recorded information is carried out by, for example, an optical heterodyne interference signal reproduction method.
For the disc type optical wave guide path recording medium, information is read out by rotating the optical wave guide path recording medium with a spindle motor. In this case, a constant linear velocity (CLV) control is needed for a high density recording medium. Further, various servo controls for a reading laser beam are necessary. Also, warps and deviations of the optical wave guide path must be limited. Therefore, the conditions for the reproduction system in the disc type optical wave guide path recording medium are very strict.
Similarly, for the card-stacked block type optical wave guide path recording medium, because the reproduction of recorded information is carried out by scanning an optical coupling portion on an end face of the optical wave guide path with a light spot, a number of mechanical parts are used and various servo controls are required just like the above-mentioned disc type optical wave guide path recording medium. Therefore, the conditions of its reproduction system are also very strict.
Accordingly, although an optical wave guide path recording medium can be easily formed in a three dimensional stacked structure and is capable of reading a large amount of information rapidly in batch at a high signal-to-noise ratio, it is very difficult to reproduce the recorded information with a high quality.